Claudiu Duma Nahid Shahmehri Patrick Lambrix A Hybrid Key Tree Scheme for Multicast to Balance Security and Efficiency Requirements. 208-213 2003 conf/wetice/2003 WETICE http://doi.ieeecomputersociety.org/10.1109/ENABL.2003.1231409 db/conf/wetice/wetice2003.html#DumaSL03